A Space Physicist

Aurora

The AuroraWatch UK alert level indicates how likely it is that an aurora will be visible from the UK.

OVATION aurora model – Northern Hemisphere

OVATION aurora model – Southern Hemisphere

The aurora (also known as the northern lights in the northern hemisphere, or southern lights in the southern hemisphere) are a beautiful display of colour in the night sky.

The aurora can occur when electrically charged particles, which originate from the Sun, are injected into the Earth’s magnetosphere and are accelerated along magnetic field lines into the Earth’s atmosphere. When in the atmosphere, some of these particles then collide with the neutral atmospheric particles – a process which transfers energy to the neutrals (either as excitation or ionisation). As a way of getting rid of this excess energy, the atmospheric particles may release a photon (light). This emission of light by the atmospheric particles is the aurora.

David St. Louis captures this shot from his front yard in Elmira, New York. https://www.flickr.com/photos/stargazerdave/

Aurora Australis (southern lights) seen from the ISS (credit: NASA)

The colour of the aurora depends upon what energy photon is released (which in turn is dependent upon the particular atmospheric particles which were collided with). The strength of the aurora is predominently dependent upon how many particles are injected into the atmosphere and how much energy they have. This is dependent on a few things, but the big thing to look out for is a geomagnetic storm.

Additionally, visibility is also affected by the time of day (i.e. you won’t see the aurora in sunlight), cloud cover, light pollution and location (generally, the nearer the Artic circle the better).

Understanding when aurora might be visible from certain locations, involves a lot of science and modelling. It is hoped that schemes like aurorasaurs will help develop our ability to give advanced notice of when and where you might be able to see nature’s magnificent light show.

For lots more information about the aurora, have a look through some of these links: